The field of the present invention is fuel pump assemblies and arrangements for fuel supply systems.
Fuel pump systems have long been known which incorporate a fuel pump located in the fuel tank of a vehicle. FIG. 5 illustrates one such device. The fuel pump, generally designated A, includes a pump body B and a pressure regulating chamber C. The pressure regulating chamber C is at the output side of the pump and is provided with a relief valve D. The relief valve D is spring biased to maintain a relatively constant fuel pressure in the regulating chamber C. The fuel pressurized by the pump B and maintained in the regulating chamber C at no more than a maximum selected pressure is delivered to a fuel pipe E which is in communciation with a carburetor or the like.
At the inlet side of the pump body B, a filter F is provided. The filter F may have a large surface area to reduce the pressure differential thereacross. The pump A may thus draw fuel from the surrounding tank through the filter F for pressurized discharge through the fuel pipe E. When fuel demand is low, fuel may pass through the relief valve D and back into the tank where it may later be drawn again through the filter F. When fuel demand is heavy, all or substantially all of the flow from the pump will pass through the fuel pipe E.
Fuels, such as gasoline, tend to easily generate vapor when the fuel temperature is elevated. In vehicles, temperature increases are experienced due to high atmospheric temperatures and radiant heat from the engine. This vapor can form bubbles in fuel system components under certain conditions. When such bubbles are present in a fuel passage, a phenomenon known as vapor lock can occur resulting in reduced or nonperformance of the system.
In fuel pumps located within the fuel tank, under conditions where vapor is easily formed, such vapor typically generated at or behind the filter, due to the differential pressure across the filter created by the resistance to flow of the fuel through the filter. Under conditions of elevated temperatures and where the filter F cannot be large enough or has been made more resistant to flow, vapor may be generated near the inlet portion G of the pump body B. Some of the vapor may be discharged through the relief valve D to harmlessly rise to the vapor phase portion of the tank. However, other vapor may be entrained in the flow through the fuel pipe E to the carburetor. The fuel through the relief valve D simply joins the remainder of the fuel in the tank such that 100% of the flow of fuel through the pump body B must pass anew through the filter F.
Another known device is illustrated in FIG. 6. In this arrangement, the pump H is also of the type contained within a fuel tank. The pump is provided with a filter portion, generally designated I, located at the intake side of the pump H. Fuel is filtered at the filter portion I through filter members J where it is then drawn into an intake port K of the pump H. The fuel is then pressurized and delivered through an exhaust port L to a carburetor or the like.
Within the filter portion I when adverse conditions exist, vapor may be generated because of the pressure differential across the filter. This generated vapor is easily drawn into the pump where it may interfere with performance of the fuel supply system. The vapor generated may find areas in the filter portion I where it may collect. Such a storage area is represented by the hatched portion M. Such vapor may accumulate under adverse conditions and eventually be drawn into the intake port K.